Improved clarifier with independent sump scraper drive

ABSTRACT

An improved clarifier tank having a rake arm assembly with one or more rake arms, a rake arm driveshaft operatively connected to the rake arms and a rake arm drive, and a sump scraper driveshaft, operatively connected to a plurality of sump scrapers and a sump scraper drive.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/516,136 filed Jun. 7, 2017, the entirety of which is hereinincorporated by reference.

FIELD OF INVENTION

The present invention relates to an improved clarifier or sedimentationthickener tank, and more particularly, to an improved clarifier tankhaving a rake arm driveshaft operatively connected to a plurality ofrake arms, and a sump scraper driveshaft, operatively connected to aplurality of sump scrapers.

BACKGROUND OF THE INVENTION

Clarifiers are commonly used in many industries to separate an influentflow containing solids materials into an underflow sludge or solidscomponent and a clarified liquid phase. Clarifier tanks conventionallycomprise a tank bounded by a concave cross-sectioned floor andupstanding wall member which together form an enclosure within which theclarification occurs via sedimentation principles. Rotatable rakemembers or the like rotate to scrape underflow, thickened sludge fromthe floor to an underflow drain or discharge line while clarified liquidat the top of the clarifier tank flows over a weir or the like forcollection.

Many of the existing conventional sump scraper design has a number ofdeficiencies. These deficiencies include:

-   -   (1) The sump scrapers rotate at the same speed as the rake arms.        As the tank diameter increases, the rake rotational speed        decreases to maintain a desired tip speed at the sacrifice of        the rotational speed of the sump scrapers. The optimum speed for        the sump scrapers is not necessarily the same speed as the rake        arms and should be faster than the rake arms.    -   (2) Rake torque is not always a good predictor of lime mud        density in the sump since the majority of the torque is        generated near the ends of the rake arms. There is currently no        way to differentiate the torque on the sump scrapers versus the        torque on the rake arms.    -   (3) The sump scrapers lift with the rake arms. When the sump        scrapers lift, they no longer sweep in front of the inlet to the        underflow pipe. This leads to erratic performance of the        underflow, typically exhibited by swings in underflow density        and flow. The term used in the industry to describe this        condition is ‘ratholing’. If the rakes remain lifted for a long        period of time, the mud in the sump can become quite hard. The        hard mud bed makes it difficult to lower the sump scrapers back        into the sump.    -   (4) There are only a few inches of clearance between the ID of        the sump and OD of the sump scrapers. If the sump scrapers are        fully lifted out of the sump, it is possible for the sump        scrapers to ‘hang’ on the top lip of the sump when lowering the        rakes. This would occur if the steady post deflects/breaks or        during other upset conditions.    -   (5) The steady post used to center the sump scrapers in the sump        is not easily replaced once installed since the post is very        long to accommodate the rake lift feature. Furthermore, lime mud        can become packed inside the vertical shaft and above the steady        post, preventing rake lowering.

SUMMARY OF THE INVENTION

In one exemplary embodiment, an improved clarifier tank is disclosed.The improved clarifier tank includes a rake arm assembly, comprising oneor more rake arms, a rake arm driveshaft operatively connected to therake arms and a rake arm drive, and a sump scraper driveshaft,operatively connected to a plurality of sump scrapers and a sump scraperdrive.

In some embodiments, the sump scraper driveshaft is nested inside therake arm driveshaft. In some embodiments, the sump scraper driveshaftand the rake arm driveshaft rotate at different speeds. In someembodiments, the sump scrapers and the rake arms rotate at differentspeeds. In some embodiments, the sump scraper driveshaft and the rakearm driveshaft rotate in different directions. In some embodiments, thesump scrapers and the rake arms rotate in different directions. In someembodiments, the sump scraper can be selected to rotate in either aclockwise or a counterclockwise direction. In some embodiments, the sumpscraper driveshaft and the rake arm driveshaft are driven by eithermechanical or hydraulic reduction.

In yet another exemplary embodiment, an improved clarifier tank isprovided. The improved clarifier tank comprises a rake arm assembly,comprising one or more rake arms; a rake arm driveshaft operativelyconnected to the rake arms and a rake arm drive; a sump scraperdriveshaft, operatively connected to a plurality of sump scrapers and asump scraper drive; and a rake arm lift device.

In some embodiments, the rake arms and the sump scrapers are separateand distinct from one another. In some embodiments, the sump scraperdriveshaft is nested inside the rake arm driveshaft. In someembodiments, the rake arm lift device lifts the rake arm drive shaft andthe rake arms without raising the sump scraper driveshaft. In someembodiments, the rake arm lift device is a dual hydraulic piston. Insome embodiments, the rake arm lift device is an electric screwassembly. In some embodiments, the rake arms and the sump scrapers areoperatively connected through a slide coupling mechanism. In someembodiments, the slide coupling mechanism allows for the rake arms tomove up-and-down, while still allowing the sump scrapers to remain in afixed position.

In yet another exemplary embodiments, an improved clarifier rankcomprises a rake arm system, comprising one or more rake arms, a rakearm driveshaft, and a rake arm drive, wherein the rake arm system is topdriven; and a sump scraper system, comprising a plurality of sumpscrapers, a sump scraper driveshaft and a sump scraper drive, whereinthe sump scraper system is bottom driven.

In some embodiments, the rake arm system is separate and independentfrom the sump scraper drive system. In some embodiments, the rake armdriveshaft is operatively connected to the rake arms and the rake armdrive. In some embodiments, the sump scraper driveshaft is operativelyconnected to the sump scrapers and the sump scraper drive, wherein thesump scraper driveshaft extends from the bottom of the clarifier tank.In some embodiments, the rake arms and the sump scrapers rotateindependently of one another. In some embodiments, the rake arms and thesump scrapers are operatively connected through a slide couplingmechanism. In some embodiments, the slide coupling mechanism allows forthe rake arms to move up-and-down, while still allowing the sumpscrapers to remain in a fixed position.

In yet another exemplary embodiment, a drive system for a clarifier tankis provided. The drive system comprises a drive assembly, wherein thedrive assembly comprises, a drive shaft, one or more rake arms, and aplurality of sump scrapers, wherein the rake arms and the sump scrapersare operatively connected to the drive shaft through a slide couplingmechanism.

In some embodiments, the rake arms and the sump scrapers are driven bythe drive assembly. In some embodiments, the rake arms and the sumpscrapers are rotated at the same speed. In some embodiments, the slidecoupling mechanism allows for the rake arms to move up-and-down, whilestill allowing the sump scrapers to remain in a fixed position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a unit storage clarifiertank in accordance with the present invention;

FIG. 2 is a schematic cross-sectional view of a unit storage clarifiertank depicting the configuration of two separate drive shafts withdrives in accordance with an embodiment of the present invention; and

FIG. 3 is schematic cross-sectional view of an improved clarifier tankin accordance with an illustrative embodiment of the disclosedtechnology; and

FIG. 4 is schematic cross-sectional view of an improved clarifier tankin accordance with an illustrative embodiment of the disclosedtechnology.

DETAILED DESCRIPTION

Turning first to FIG. 1 of the application, a clarifier unit 2 of thetype commonly used in the clarification of green liquor in arecausticizing process is shown. It is noted that this unit's storagetype clarifier tank differs from a standard clarifier tank by havingstorage capacity for clarified liquid. It should be understood by aperson of ordinary skill in the art that the term clarifier andsedimentation thickener can be used interchangeably.

The clarifier unit 2 includes a tank 4 having a continuous wall member14 and a bottom 6. The wall and bottom define a volume enclosure withinwhich a liquid containing solids particulate matter is separated intoclarified liquid and liquid/solid phases. As shown, the bottom 6 isconcave in cross-section with the nadir of the bottom terminating in adrain 10 and associated drain line 12 through which solids, underflowmaterial will be removed.

An influent pipe 16 is provided in communication with inlet 22 toprovide influent feed to a feedwell 24. As shown, the feedwell is of thetype having a roof 26 and continuous wall 28 depending therefrom to forma feedwell enclosure. It should be understood by one skilled in the artthat the feedwell 24 may include any conventional feedwell design andmay include a number of additional features.

The clarifier unit 2 of the present invention includes two separatedrive shafts, a rake arm drive shaft 30 and a sump scraper drive shaft31, whereas the sump scraper drive shaft 31 is nested within the rakearm drive shaft 30. In some embodiments, the rake arm drive shaft 30encompasses the sump scraper drive shaft 31. In other embodiments, therake arm drive shaft 30 includes an internal sleeve, where having aninternal opening adapted to fit over said sump scraper drive shaft 31.In other embodiments, the sump scraper drive shaft 31 is encapsulated bythe rake arm drive shaft 30 by other conventional means.

As shown in FIG. 1, a rake assembly 8 is operatively connected to therake arm drive shaft 30. The rake assembly 8 generally comprises one ormore rake arms 8 a which rotate about the central axis of the tank 4.The rake arms 8 a are attached to the rake arm drive shaft 30 so as torotatably scrape the underflow sludge from the bottom of the tank.Additionally, the sump scraper drive shaft 31 is operatively connectedto a plurality of sump scrapers 35.

In some embodiments, the rake arm drift shaft 30 is driven via the rakearm drive 32 that may be, as is shown in FIG. 1, supported by bridgemember 34. Stabilizer cables 36 and 38 suspend the feedwell from thetank and the bridge member respectively. A weir 40 is provided tocollect clarified liquor. Further, the clarifier unit may be providedwith a vent line 42, coaxially disposed about the shaft 30. A roof 74 isprovided over the tank and, as shown, the liquor level in the tank isshown at 76.

In some embodiments, the rake arm drive shaft 30 is operativelyconnected to a rake arm drive 32, and the sump scraper drive shaft 31 isoperatively connected to a sump scraper drive 33. These separate drivescan be separately driven by either mechanical or hydraulic reduction, oralternatively, by means of the like.

Referring now to FIG. 2, the rake arm drive shaft 30 is operativelyconnected to a rake arm lift device 37. The rake arm lift device 37provides a lifting feature that allows for the rake arms 8 a to lift orbe raised independently. In some embodiments, the rake arm lift device37 is a dual hydraulic piston, or the like. As such, the rake arms 8 a,including the rake arm drive shaft 30, can be raised without raising thesump scraper drive shaft 31 or the sump scrapers 35. One advantage ofproviding the separate rake arm drive 32 and a separate sump scraperdrive 33 is that each can be run at optimized speeds and yet still allowthe sump to remain agitated even while the rake arm lift device is inoperation.

In some embodiments, the sump scrapers 35 can be rotated at a differentspeed than the rake arms 8 a. In some embodiments, the sump scrapers 35are rotated at a faster speed than the rake arms 8 a. By optimizing thespeed of the rake arms 8 a, it allows additional thickening to takeplace and maintain a more uniform, homogenous density in the sump. Insome embodiments, torque feedback direct from the sump scrapers 35 canbe used to optimize underflow density control.

In some embodiments, the sump scrapers 35 are able to rotate in either aclockwise or counterclockwise direction. Depending on the ‘fish mouth’orientation of the underflow pipes, the ability to rotate in eitherdirection is beneficial to better distribute wear on the sump scrapers35.

In some embodiments, the rake arms 8 a and the sump scrapers 35 areseparate and distinct from one another. Because the rake arms 8 a andthe sump scrapers 35 are separate and distinct from one another, oneadvantage is that the sump scrapers 35 will no longer lift with the rakearms 8 a. This advantage gives the operators the ability to betterutilize the mud storage capacity of the thickener while simultaneouslykeeping the sump scrapers sweeping in front of the inlet to theunderflow pipe at all times to prevent ratholing. This is particularlyimportant under upset conditions that may cause the rake arms to raisequickly and unexpectedly (e.g. slaking large quantities of purchasedlime, overliming, interruption in downstream operations, etc.). Becausethe sump scrapers 35 will no longer lift with the rake arms 8 a, it alsoeliminates the issues of having to lower the sump scrapers into a hardmud bed in the sump or having the sump scrapers hang on the edge of thesump during rake arm lowering.

In a preferred embodiment, the clarifier comprises a rake arm system A(which is top driven), and a sump scraper system B (which is bottomdriven). As shown in FIG. 3, where like parts have like numerals tothose in FIGS. 1 and 2, plus 100, the rake arm system A provides therake arms 108 a, the rake arm drive shaft 130, and a rake arm drive (notshown in figure). The sump scraper system B provides the sump scrapers135, the sump scraper drive shaft 131, and an independent and separatesump scraper drive 140, which is located at and driven from the bottomof the clarifier. The sump scraper drive 140 is operatively connected tothe sump scraper drive shaft 131, where the sump scraper drive shaft 131extends from the bottom of the clarifier. In some embodiments, the sumpscraper drive 140 may also act as a steady post for the top driven, rakearm drive system.

In some embodiments, the rake arms 108 a are operatively connected to arake arm drive shaft 130, and the sump scrapers 135 are operativelyconnected to a sump scraper drive shaft 131, allowing for the rake arms108 a and the sump scrapers 135 to rotate independently of one another.

In yet another preferred embodiment, the sump scrapers can be rotated atthe same speed as the rake arms, but yet the sump scrapers do not liftwith the rake arms. As shown in FIG. 4, where like parts have likenumerals to those in FIGS. 1-3, plus 100, in some embodiments, theimproved clarifier includes a single drive assembly comprising a driveshaft 200, where the rake arms 208 a and sump scrapers 235 areoperatively connected to the drive shaft 200 through a slide coupling240. The single drive assembly further comprises a steady post 242 and asump scraper retainer 244.

In some embodiments, the rake arms 208 a and the sump scrapers 235 aredriven by the single drive assembly and are rotated at the same speed.The slide coupling 240 allows for the rake arms 208 a to moveup-and-down to adjust to varying mud levels, yet still allows the sumpscrapers 235 to remain in a fixed position and rotate at the same speedas the rake arms 208 a. During operation of or the up-and-down movementof the rake arms 208 a, the sump scrapers 235 remain locked in place,where the combination of the steady post 242 and the sump scraperretainer 244 provide a steady post feature that retain the sump scrapers235 in place.

While certain embodiments of the invention have been shown and describedherein, it is intended that there be covered as well any change ormodification therein which may be made without departing from the spiritand scope of the invention as defined in the appended claims.

1. An improved clarifier tank, comprising: a rake arm assembly,comprising one or more rake arms; a rake arm driveshaft operativelyconnected to said rake arms and a rake arm drive; and a sump scraperdriveshaft, operatively connected to a plurality of sump scrapers and asump scraper drive.
 2. The clarifier as in claim 1, wherein said sumpscraper driveshaft is nested inside said rake arm driveshaft.
 3. Theclarifier tank as in claim 1, wherein said sump scraper driveshaft andsaid rake arm driveshaft rotate at different speeds.
 4. The clarifiertank as in claim 1, wherein said sump scrapers and said rake arms rotateat different speeds.
 5. The clarifier tank as in claim 1, wherein saidsump scraper driveshaft and said rake arm driveshaft rotate in differentdirections, and wherein said sump scrapers and said rake arms rotate indifferent directions.
 6. (canceled)
 7. The clarifier tank as in claim 1,wherein said sump scraper can be selected to rotate in either aclockwise or a counterclockwise direction.
 8. The clarifier tank as inclaim 1, wherein said sump scraper driveshaft and said rake armdriveshaft are driven by either mechanical or hydraulic reduction.
 9. Animproved clarifier tank, comprising: a rake arm assembly, comprising oneor more rake arms; a rake arm driveshaft operatively connected to saidrake arms and a rake arm drive; a sump scraper driveshaft, operativelyconnected to a plurality of sump scrapers and a sump scraper drive; anda rake arm lift device.
 10. The clarifier tank as in claim 9, whereinsaid rake arms and said sump scrapers are separate and distinct from oneanother.
 11. The clarifier tank as in claim 9, wherein said sump scraperdriveshaft is nested inside said rake arm driveshaft.
 12. The clarifiertank as in claim 9, wherein said rake arm lift device lifts said rakearm drive shaft and said rake arms without raising said sump scraperdriveshaft.
 13. The clarifier tank as in claim 9, wherein said rake armlift device is a dual hydraulic piston, or an electric screw assembly.14. (canceled)
 15. The clarifier tank as in claim 9, wherein said rakearms and said sump scrapers are operatively connected through a slidecoupling mechanism, wherein said slide coupling mechanism allows forsaid rake arms to move up-and-down, while still allowing said sumpscrapers to remain in a fixed position.
 16. (canceled)
 17. An improvedclarifier tank, comprising: a rake arm system, comprising one or morerake arms, a rake arm driveshaft, and a rake arm drive, wherein saidrake arm system is top driven; and a sump scraper system, comprising aplurality of sump scrapers, a sump scraper driveshaft and a sump scraperdrive, wherein said sump scraper system is bottom driven.
 18. Theclarifier tank as in claim 17, wherein said rake arm system is separateand independent from said sump scraper drive system.
 19. The clarifiertank as in claim 17, wherein the rake arm driveshaft is operativelyconnected to said rake arms and said rake arm drive.
 20. The clarifiertank as in claim 17, wherein said sump scraper driveshaft is operativelyconnected to said sump scrapers and said sump scraper drive, whereinsaid sump scraper driveshaft extends from the bottom of the clarifiertank.
 21. The clarifier tank as in claim 17, wherein said rake arms andsaid sump scrapers rotate independently of one another.
 22. Theclarifier tank as in claim 17, wherein said rake arms and said sumpscrapers are operatively connected through a slide coupling mechanism,wherein said slide coupling mechanism allows for said rake arms to moveup-and-down, while still allowing said sump scrapers to remain in afixed position.
 23. (canceled)
 24. A drive system for a clarifier tank,the drive system comprising: a drive assembly, wherein said driveassembly comprises, a drive shaft, one or more rake arms, and aplurality of sump scrapers, wherein said rake arms and said sumpscrapers are operatively connected to said drive shaft through a slidecoupling mechanism, wherein said slide coupling mechanism allows forsaid rake arms to move up-and-down, while still allowing said sumpscrapers to remain in a fixed position. 25-27. (canceled)